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Infrared chlorophyll could boost solar cells

Nature still has plenty to teach us about harnessing the sun's energy.
The latest lesson comes from the ancient stromatolites living in
Australia's Shark Bay. Their cyanobacteria contain a newly discovered
form of chlorophyll – the fifth known – that absorbs sunlight in the red
and infrared part of the spectrum. It could be harnessed to help solar
cells convert more light into electricity.

Stromatolites are among the most primitive of life forms, with a
fossil record stretching back over 3.4 billion years. Their layered
structures are built up by sediment-trapping cyanobacteria.
Stromatolites suffered markedly with the evolution of animals that
munched on the defenceless algal mats, and are now found only in
inhospitable environments where such animals are rare – including the
very salty Shark Bay.

Min Chen of the University of Sydney in Australia, and her
colleagues, went looking for interesting chlorophyll in the
stromatolites there because the water in which they live – and the
trapped sediment that bulks them out – filter out much of the visible
light reaching the stromatolitic cyanobacteria. The team suspected that
the cyanobacteria might therefore be better-than-average at absorbing
the infrared radiation that makes it through.

Their hunch proved correct, but rather than familiar chlorophyll in
new formations, they found a completely new type of chlorophyll –
chlorophyll f – made by an as-yet unnamed filamentous bacterium.